Ionization Gap Research Articles

PICOSEC-Micromegas Detector, an innovative solution for Lepton Time Tagging

The PICOSEC-Micromegas (PICOSEC-MM) detector is a novel gaseous detector designed for precise timing resolution in experimental measurements. It eliminates time jitter from charged particles in ionization gaps by using extreme UV Cherenkov light emitted in a crystal, detected by a Micromegas photodetector with an appropriate photocathode. The first single-channel prototype tested in 150 GeV/c muon beams achieved a timing resolution below 25 ps, a significant improvement compared to standard Micropattern Gaseous Detectors (MPGDs). This work explores the specifications for applying these detectors in monitored neutrino beams for the ENUBET Project. Key aspects include exploring resistive technologies, resilient photocathodes, and scalable electronics. New 7-pad resistive detectors are designed to handle the particle flux. In this paper, two potential scenarios are briefly considered: tagging electromagnetic showers with a timing resolution below 30ps in an electromagnetic calorimeter as well as individual particles (mainly muons) with about 20ps respectively.

The Influence of the Side Chain Structure on the Photostability of Low Band Gap Polymers.

Side chains play an important role in the photo-oxidation process of low band gap (LBG) polymers. For example, it has been shown that their photostability can be increased by the introduction of aromatic-oxy-alkyl links. We studied the photostability of prototypical LBG polymers with alkyl and oxyalkyl side chains during irradiation with white light (AM 1.5 conditions) in dry air using UV/vis and IR spectroscopy. Though its degradation kinetics were distinctly affected by the presence or absence of oxygen in the structure of the side chains, in particular cases, the stability was more affected by the presence of linear or branched side chains. Moreover, we showed that the exact position of the alkyl/oxyalkyl side chain at the polymer backbone could be crucial. Although minor effects of chemical modifications on the electronic parameters (ionization potential and gap) were observed, the molecular orientation, determined by polarization modulation-infrared reflection-absorption spectroscopy (PMIRRAS), could be affected. The aggregation and crystallinity of these polymers may distinctly affect their stability.

The conformational control of small D-A-D organic solar cells for large power conversion efficiency: A deep quantum chemistry analysis

Four naphthalene diimide (NDI) based small organic solar cells have been studied with for photoexcited and photovoltaic properties. Density functional theory and Tamm-Dancoff Approximation (TDA) with range-separation gap tunning have been used for ground and excited state calculations. The theoretical calculated results are highly reliable as the difference between the fundamental energy gap (Eg) and ionization gap (Ig) are nearly same. During this research study, the positions of donor units changed with symmetrical and unsymmetrical attachment sites which produced the interesting results of optoelectronic properties at both ground and excited states. The triphenyl amine (TPA) donor units at unsymmetrical units de-stabilized the HOMO and stabilized the LUMO energy levels significantly. The small vertical excitation energies of NDI-TPA molecules increased the transition coefficients from HOMO to LUMO. The emission rate of electron from S1 excited state to S0 is large for DPA-based molecules due to large vertical emission oscillator strength.

Recommendation of Orbitals for G0W0 Calculations on Molecules and Crystals

The many-body GW approximation, especially the G0W0 method, has been widely used for condensed matter and molecules to calculate quasiparticle energies for ionization, electron attachment, and band gaps. Because G0W0 calculations are well-known to have a strong dependence on the orbitals, the goal of the present work is to provide guidance on the choice of density functional used to generate orbitals and to recommend a choice that gives the most broadly accurate results. We have systematically investigated the dependence of G0W0 calculations on the orbitals for 100 molecules and 8 crystals by considering orbitals obtained with a diverse set of Kohn-Sham (KS) and generalized KS (GKS) functionals (63 functionals plus Hartree-Fock). The percentage of Hartree-Fock exchange employed in density functionals has been found to have strong influence on the predicted molecular ionization energy and crystal fundamental band gaps (with optimum values between 40 and 56%), but to have less effect on predicting molecular electron affinities. The low cost of the Gaussian implementation, even with hybrid functionals in periodic calculations, the better performance of global hybrids as compared to range-separated hybrids of either than screened exchange or long-range-corrected type, and the relatively low cost of global-hybrid-functional periodic calculations using Gaussians means that one can employ global-hybrid functionals at a very reasonable cost and obtain more accurate band gaps of semiconductors than are obtained by the methods currently widely employed, namely local gradient approximations. We single out three global-hybrid functionals that give especially good results for both molecules (100 in the test set) and crystals (8 in the test set, for all of which our benchmark data are the proper band gap rather than an optical band gap uncorrected for exciton effects).

Ionization Gas Sensor using Suspended Carbon Nanotube Beams.

An ionization sensor based on suspended carbon nanotubes (CNTs) was presented. A suspended CNT beam was fabricated by a low-temperature surface micromachining process using SU8 photoresist as the sacrificial layer. Application of a bias to the CNT beam generated very high non-linear electric fields near the tips of individual CNTs sufficient to ionize target gas molecules and initiate a breakdown current. The sensing mechanism of the CNT ionization sensor was discussed. The sensor response was tested in air, nitrogen, argon, and helium ambients. Each gas demonstrated a unique breakdown signature. Further, the sensor was tested with gaseous mixtures. The sensor exhibited good long-term stability and had comparable performance to other reported CNT-based ionization sensors in literature, which use high-temperature vapor deposition methods to grow CNTs. The sensor notably allowed for lower ionization voltages due to its reduced ionization gap size.

Investigation into the transient flow characteristics of noble gas propellants using the pulsed inductive discharge in electric propulsion

The Pulsed Inductive Thruster (PIT) has the advantages of repeatable startup, no corruption and in-situ propellant feed. To study the flow expansion and circuit characteristics of PITs, the circuit-fluid model is developed, and the high temperature thermodynamic and transport models are combined with the circuit-fluid model to predict the critical plasma parameters. The flow fields of initial mass of 2–8 mg and charge voltages of 10–14 kV are simulated. Comparison of the flow fields of argon and helium propellants suggests that, the flow field structures are similar. Slight differences exist on the magnitude of the density and magnetic field, caused by larger velocity in lighter atom case and difference on the ionization gap between adjacent ionization levels. Analysis of the circuit characteristics by the two-dimensional results indicates that the ratio of coil inductance to circuit inductance affects both the rise rate and phase of the plasma current, the larger the ratio, the greater the rise rate and the better the following characteristic. The calculations show that the magnetic energy obtained within the decoupling distance determines the overall performance the thruster can be obtained; self-induced field maintained by the thermal motion after the main pulse leads to the long attenuation process and difference on the total impulse when the angle of conical pylon is varied under constant coil dimension.

Measurements of flame propagation in a rotary engine using rotor-installed ionization gaps

The combustion in a rotary engine has been investigated in terms of the flame propagation on the rotor flank and the information obtained simultaneously from the working chamber pressure. An experimental overhanging eccentric shaft-type single rotor engine was used, which was equipped with a multichannel packaged slip ring to take out the signals of 15 uniformly-spaced ionization gaps on the rotor flank. The measurements were made under the experimental conditions of various air fuel ratios, ignition modes (leading spark plug only and trailing spark plug only, dual spark plugs and triple spark plugs) and intervals between leading and trailing spark timings. The effects of flame propagation patterns on P-V diagrams, heat release rates, indicated mean effective pressures and indicated specific fuel consumption ratios are discussed. The flame propagation at the center in the rotor width direction was found to occur in order of the front part, the rear part, the center part of the rotor recess, the front part of the leading side of the rotor, and the rear part of the trailing side. Also the flame could propagate to both corners on the rear part of the trailing side of the rotor later than 150°ATDC.

Sensitivity of modeled microscale gas breakdown voltage due to parametric variation

Device miniaturization increases the importance of understanding and predicting gas breakdown and electrical discharge thresholds. At gap sizes on the order of ten microns at atmospheric pressure, field emission drives breakdown rather than Townsend avalanche. While numerical and analytical models can demonstrate this transition, a quantitative understanding of the relative importance of each parameter remains unclear. Starting from a universal model for gas breakdown across the field emission and Townsend avalanche regimes [A. M. Loveless and A. L. Garner, Phys. Plasmas 24, 113522 (2017)], this paper applies the concept of error propagation from ionizing radiation measurements to determine the relative impact of each factor on the predicted breakdown voltage. For limits of both large and small products of the dimensionless ionization coefficient, α¯, and gap distance, d¯, the electrode work function has the largest relative effect on the predicted breakdown voltages with a deviation of 50% in the work function resulting in an uncertainty in the calculated breakdown voltage of ∼84% for both α¯d¯≫1 and α¯d¯≪1. This quantifies the significance of nonuniformities in material surfaces and changes in the surface structure during multiple electric field applications and help predict the breakdown voltage for small gaps, motivating better electrode characterization both initially and during repeated operation.

Results and performances of X-ray imaging GEM cameras on FTU (1-D), KSTAR (2-D) and progresses of future experimental set up on W7-X and EAST Facilities

The triple Gas Electron Multiplier (GEM) is a good candidate for the observation of the plasma volume emitting X-rays photons in the energy band up to 30 keV . The GEM camera system can be simply installed outside the port of a fusion device and it's a micropattern proportional gas detector which consists of an ionization gap, where X-rays photon conversion occurs, three consecutive foils working as amplification stage and finally a dedicated printed circuit board. Its simple experimental setup can be made in different configurations with 1D or 2D imaging possibilities: perpendicular GEM camera allows a 1D emissivity profile reconstruction instead a tangential GEM camera allows a poloidal cross-section image. Moreover, they offer high sensitivity, noise free, optical flexibility (zooming and tilting, magnification 10× up to 30×), high contrast, high dynamic range (6 orders of magnitude) and good time resolution (submillisecond). In this work several experimental results already observed on the Frascati Tokamak Upgrade (FTU) and the Korean Superconducting Tokamak Advanced Research (KSTAR) devices will be presented. The perpendicular installation on FTU allows a 1D radial profile with 128 lines of sight, while thanks to the 2D tangential view of the plasma, the reconstruction of the cross section has been done on KSTAR. Between them there are dynamic and precursors of sawtooth, effects of Edge Localized Mode (ELM) in the core and possible interplay between core and edge in ELMs (high m modes), effects of plasma rotation in the core, dynamic of injected impurities in the outer part of the plasma or also impurity accumulation and localized effects of additional heating. Installation of GEM systems is planned on Wendelstein 7-X (W7-X) and the Experimental Advanced Superconducting Tokamak (EAST) also for their robustness and flexibility X-rays detection in presence of high radiative environments (neutrons and gammas). In future applications on the above mentioned fusion devices, another possibility under evaluation is to use standard tomographic methods using two orthogonal GEM camera systems.

Cosmic ray test of mini-drift thick gas electron multiplier chamber for transition radiation detector

A thick gas electron multiplier (THGEM) chamber with an effective readout area of 10×10cm2 and a 11.3mm ionization gap has been tested along with two regular gas electron multiplier (GEM) chambers in a cosmic ray test system. The thick ionization gap makes the THGEM chamber a mini-drift chamber. This kind mini-drift THGEM chamber is proposed as part of a transition radiation detector (TRD) for identifying electrons at an Electron Ion Collider (EIC) experiment. Through this cosmic ray test, an efficiency larger than 94% and a spatial resolution ~220μm are achieved for the THGEM chamber at −3.65kV. Thanks to its outstanding spatial resolution and thick ionization gap, the THGEM chamber shows excellent track reconstruction capability. The gain uniformity and stability of the THGEM chamber are also presented.

Multichannel wire gas electron multipliers

A simple technique for manufacturing electrodes of multichannel wire gas electron multipliers was developed. The maximum proportional multiplication factor of ionization electrons Kmax = 103 was obtained when the chamber containing a multichannel wire gas electron multiplier was filled with a mixture of Ar + 10%C2H4 at a pressure of 1 atm (abs.) and the drift (ionization) gap of the chamber was irradiated with β particles (63Ni). Under irradiation with α particles, Kmax = 103 at a pressure of 1 atm (abs.) and 3 × 103 at 0.4 atm (abs.). When the chamber was filled with a mixture of Ne + 10%C2H4 at a pressure of 1 atm (abs.) and exposed to β particles, Kmax = 4 × 103 was obtained.

Optical and electrical characteristics of poly(3-alkylthiophene) and polydiphenylamine copolymers: Applications in light-emitting devices

In this work, poly (3-methylthiophene) (P3MT) or poly (3-octylthiophene) (P3OT) films were synthesized electrochemically with polydiphenylamine (PDFA), in layers and blended copolymers, in non-aqueous media through the oxidation of the monomers, using a standard three-electrode cell in acetonitrile with 0.100molL−1 LiClO4. The polymeric thin films were deposited on platinum plates for optimal quality control of the process. The electrochemical behaviors of as-prepared and partial dedoped films obtained by these methods was verified by cyclic voltammetry (CV) and have been characterized by UV–vis reflectance, resonance Raman, electron paramagnetic resonance (EPR) and photoluminescence (PL) spectroscopy. Based on data obtained by UV–vis reflectance spectroscopy, it was possible to characterize the chemical species in the polymer matrix using the resonant Raman method. Both Raman and PL spectra results led to the characterization of three structures (aromatic, semi-quinone and quinone forms of thiophene rings) which formed the homopolymers and copolymers chain. The EPR measurements were taken to quantify the semi-quinone species stabilization at 298 and 77K temperatures. The ionization potential (IP), electron affinity (E.A.) and gap energy (Eg) parameters were determined based on the technical analyses carried out.

Upgrade Plans for ATLAS Forward Calorimetry for the HL-LHC

Abstract Even though the LHC is still in an early phase of operation, plans are being developed to operate the machine and its detectors at up to 10 times the original design luminosity. This has a major impact on the Forward Calorimeter (FCal), which is exposed to some of the highest radiation rates in ATLAS. The FCal detector and its associated components were designed for operation at the maximum LHC luminosity of 1034 cm-2s-1. However at the higher luminosities projected for the HL-LHC, operation of the FCal may be compromised. Beam heating in the FCal could lead to the formation of argon bubbles in the detector, the ionization rate will result in space charge effects that will reduce the signal and the current draw will result in a voltage drop across the HV current limiting resistors. Two possible solutions are being considered to maintain FCal operation at HL-LHC. One is a complete replacement of the FCal system. A replacement FCal would have a similar design to the current calorimeter except for the addition of cooling loops, lower value HV protection resistors and the use of smaller ionization gaps, as small as 100 microns in the first compartment. The second solution is the installation of a small warm calorimeter, referred to as the Mini-FCal, to be placed in front of the FCal. This addition would reduce the ionization load in the first FCal compartment, which would keep a larger region of the FCal active and reduce the heat load to an acceptable level. The current concept for the Mini-FCal is a standard parallel plate calorimeter with copper absorbers and diamond sensors, which were chosen for their inherent radiation resistance. It is anticipated that neutrons will be the major cause of damage to the diamond sensors and the integrated flux of neutrons in the Mini-FCal after 3000 fb-1 at the HL-LHC will be up to 2 x 1017 neutrons/cm2. Recent irradiation tests carried out by members of the ATLAS Liquid Argon group show that these sensors can still operate after irradiation up to these levels although with a large reduction in signal.

Bistable Charge Configuration of Donor Systems near the GaAs(110) Surfaces

In gated semiconductor devices, the space charge layer that is located under the gate electrode acts as the functional element. With increasing gate voltage, the microscopic process forming this space charge layer involves the subsequent ionization or electron capture of individual dopants within the semiconductor. In this Letter, a scanning tunneling microscope tip is used as a movable gate above the (110) surface of n-doped GaAs. We study the build-up process of the space charge region considering donors and visualize the charge states of individual and multi donor systems. The charge configuration of single donors is determined by the position of the tip and the applied gate voltage. In contrast, a two donor system with interdonor distances smaller than 10 nm shows a more complex behavior. The electrostatic interaction between the donors in combination with the modification of their electronic properties close to the surface results in ionization gaps and bistable charge switching behavior.

IONIZATION BY QUANTIZED ELECTROMAGNETIC FIELDS: THE PHOTOELECTRIC EFFECT

In this paper, we explain the photoelectric effect in a variant of the standard model of non relativistic quantum electrodynamics, which is in some aspects more closely related to the physical picture, than the one studied in [5]. Now, we can apply our results to an electron with more than one bound state and to a larger class of electron-photon interactions. We will specify a situation, where the second order of ionization probability is a weighted sum of single photon terms. Furthermore, we will see that Einstein's equality [Formula: see text] for the maximal kinetic energy E kin of the electron, energy hν of the photon and ionization gap △E is the crucial condition, for these single photon terms to be nonzero.

Diffusion correction to the Raether–Meek criterion for the avalanche-to-streamer transition

Space-charge dominated streamer discharges can emerge in free space from single electrons. We reinvestigate the Raether–Meek criterion and show that streamer emergence depends not only on ionization and attachment rates and gap length, but also on electron diffusion. Motivated by simulation results, we derive an explicit quantitative criterion for the avalanche-to-streamer transition both for pure non-attaching gases and for air, under the assumption that the avalanche emerges from a single free electron and evolves in a homogeneous field.

平たんバーナ低温度炎におけるすす前駆物質の生成(燃焼反応とPM問題,内燃機関の燃焼化学と排出物制御)

The formation of polycyclic aromatic hydrocarbons (PAHs) and ion has been studied on the laminar, diethyl-ether/air premixed low-temperature flames under atmospheric pressure and the equivalence ratio ranging from 3.0 to 6.0, to obtain an advanced knowledge of soot formation processes. A flat-burner is enclosed by a concentric quatz tube to prevent infiltration of surrounding air. Ion formation is recognized to be related to soot precursor formation. The ion current has been measured using an ionization gap. A liquid chromatograph with a fluorescence detector was applied to separate and determine PAHs contained in specimens sampled from low-temperature flames. PAHs was obtained by microwave extraction of soluble organic fraction (SOF) on silica glass filters. It is indicated a possibility that the ion is generated from the exited oxygen molecules and acetylene generation due to the interrelation between ion current and light emission. It has also been found that the PAHs first appears during the cool flame period.

Recent measurements of flame acceleration in semiconfined geometries

Abstract Turbulent premixed combustion under certain conditions may lead tolarge flame speeds sufficient to cause significant damage to nearby structures. Experiments, both large and small scale, have confirmed that obstructions cause severe flame acceleration to occur. In these cases, flame speeds as high as 800 ms−1 may be achieved. In this work experimental investigation of some factors affecting flame acceleration in a semiconfined channel has ben carried out. The experimental facility and the developed ionization gap measuring technique are also described. It has been found that the presence of obstacles, degree of confinement, heiht of fuelair cloud (FAC), as well as fuel concentration gradient in the FAC have profound effects on the rate at which the flame accelerates. Finally, consideration of the flame acceleration as a possible mechanism for the transition to detonation will be discussed.

Ion formation in compression ignition low-temperature flames.

Ion forrmation is detected for the first time in cool and blue flames which appear during the preflame period for compression ignition of a heptane / air mixture. A rapid-compression machine is used for mixture compression and an ionization gap is installed in the combustion chamber. Ion current and emission of active species are observed simultaneously. Ions arise at the time the cool flame degenerates, and the ion current itself will degenerate very late in the blue-flame induction time τ2 just before the blue-flame onset. The behavior of ion-current appearance in a cool flame shows the possibility that the ion is mutually related to the emission of excited oxygen molecules and the generation of olefin. During the blue-flame period the ion current is always detected more definitely. Degeneration of the ion current is often observed late in the blue-flame period. The occurrence of ion-current degeneration after the blue flame comes about can be recognized as a prognostication for the development up to the final real ignition.

Electrostatic Probe Measurements in Propagating Flames : Part 1, The Relation between Flame Front Configuration and Ion Current

An experimental study has been made for ascertaining the relation between the combustion phenomena of a propagating flame and the ion current from the flame to an electrostatic probe or ionization gap. A schlieren system was simultaneously used together with the electrostatic probe to study a flame propagating through a stoichiometric propane-air mixture in a closed combustion tube in the initial pressure range from 100 to 600 mm Hg. It was found that the flame front might be disturbed by the turbulence of the unburned gas flow. The measured distance between the locations of schlieren front and maximum ion current lay in the range from 2 to 6 mm. When the flame front was disturbed, the ion current fluctuations were observed. These ion current of the flame front and were inferred to be closely to the flame front configuration.